Stoker control switch



Jan. 3, 1939. L, R TEEPLE sToKER CONTROL swITcH Filed Dec. 27, 1935 3 Sheets-Sheet l MEA/TUR L. Y2 .TEEPLE /4 TTDRA/W IIIIIIIIH Jan. 3, 1939. L, R, TEEPLE 2,142,462

STOKER CONTROL SWITCH Filed Dec. 27, 1935 3 SheebS-Sheeb 2 7- TUR N55/ s sheets-sheet 3 .5A/TUR L. RTEEPLE En/ Jan. 3, 1939. 1 R TEEPLE sToKER CONTROL swITCH Filed Dec. 27, 1935 Patented Jan, 3, 1939 NITED STATES PATENT OFFICE 19 Claims.

This invention relates generally to controls for coal burning stokers, and particularly to a stoker control switch.

'Ihe main object of this invention is the combining of a timer and a stack thermostat for refueling a stoker whereby the timing mechanism is reset to an initial position at the end of each stolzer operation and subsequently turns on the stoker for refueling after a given interval in 1() which no operation occurs and discontinues the operation of the stoker on a rise of stack temperature resetting same to the initial position and conclusively. stops the stoker if the tempera.- ture of the stack does not rise before the end of a given period of stoker operatiom The second object of this invention is the provision of a stoker control switch whereby any stoker operation intiated by a. thermostat immediately suspends the timed refuelingoperation completely until the thermostat has shut dif the stoker and reset the timingmechanism and in which the period f operation permitted the stoker before conclusively shutting it off on'absence of fire is always the same regardless of whether the operation is initiated by the thermostat orthe timing device.

The third object is to improve the switch described in my Reissue Patent No. 19,164 in which ire rekindling operations are xed in length by 3o a definite time setting. The present invention adds fire-out ,operation from time and stack and limits the length of the rekindling, operation from a stack temperature rise.

` The fourth object is to improve the `device de- 3'5 'scribed in my application, Serial No. 661,452, Pat- .fent No. 2,119,187, May 31, 1938, by timing the idle period before^ a rekindling operation from the stolzer-shut oi instead of from the temperature-drop and by adding outre protection.

The ith object is to improve the device described in my Patent No. 1,973,128 by adding the fire-out operation and limiting the rekindlingy from the rise instead-of from the fixed stack temperature and by spacing the rekindling operation from the end of the previous stoker operation.

The sixth object is to improve the4 device described in application, Serial No. 27,275 by spacing'the rekindling operation from a stoker shutdown and limiting the length of the rekindling operation from the rise' of the stack temperature instead of from a Ixed setting and shutting of! conclusivelyl if no riseof stack temperature occurs in a given time instead of being dependent on actual value of stack temperature with respect to a setting.

The seventh object is to provide a device of the class described which includes indicating dials and pointers, the positions of which will show the state of and reason for the operation or inoperation of the stoker. k

The eighth object is the intermittent determination of the position of the room thermostat and if that position shows that a turn on or turn off operation is approaching, it will execute the operation in advance of the thermostat.

The ninth object is to utilize the desirable features of a switch, the operation or inoperation of which is determined by the relative positions of a plurality of cams with respect to each other, as well as by the relative position of each or all oi them with respect to the switch member.

I accomplish these and other objects in the manner set forth in the following speciiication as illustrated in the accompanying drawings, in which:

Fig. 1 is a side elevation, partly in section.

Fig. 2 is a section taken along the line 2-2 in Fig. 1. I

Fig. 3 is a front elevation of the switch.

Fig. 4 is a rear elevation showing the contact plate for the out, on, and refueling circuits.

Fig. 5 is a fragmentary perspective view showing the construction'of the refueling and fireout switches.

Fig. 6 is a diagram showing the various circuits in a position in which it is assumed that a refueling operation has just been initiated by the timing device, the room is warm, the stack cool, and the stoker running.

Fig. 7 is similar to Fig. 6, but showing the l stoker just turned on by the room thermostat with the stack still cool.

Fig. 8 is similar to Fig. 7 with the parts in an assumed position in which the fire has gone out and the stack is cool and in which the dial following a measured period of operation has moved to the outposition in which no operation can be started by the device itself or by the thermostat unless the fire is first lighted manually and vthe stack heated thereby or the dial is turned manually.

Fig. 9 is similar to Fig. 8 showing the parts in position just after a normal shutting off of the stoker with the stack hot and the room warm.

Similar numbers of reference refer to similar parts throughout the several views.

Referring in detail to the mechanism, same will be seen to include a back plate I0 behind which 55 is mounted the slow speed timing motor II and the high speed switch operating motor I2, these being of the synchronous type and of a size suitable for the purpose intended. In front of the plate I and spaced therefrom by the pillars I3 is a front plate I4. Journaling in the plates I8 and I4 is a time drive shaft I5.

A pointer I6 is secured to the shaft I5 in front of the plate I4. Secured on the shaft I5 between the plates I0 and I4 is the switching `cam I1, a, main time drive gear I6 and a ratchet pawl arm I9, whose pawl is provided with an outwardly extending end 2l which can engage a roller 22 mounted on the rear of thelplate I4 when the arm lis sufficiently rotated so as to lift pawl 20 when the arm I9 has'rotated 180 from the posi-v tion shown in Figure 2.

Between the cam I1 and the gear I8 is disposed a cam gear 23 which is revolvable with relation to the shaft I5. Secured to the gear 23 is a cam 24.

Between the gear I8 and the arm I9 is the ratchet wheel gear 25 which carries the ratchet wheel 26. The ratchet wheel gear 25 is driven positively by the timing motor II through the reduction gears 21.

, The cam I1 is driven by the timing motor II at a Aspeed which in this case is two hours per revolution. This cam I1 has approximately ninety degrees cf its outer surface cut away, while the cam 24 which is driven at a much higher speed, namely one revolution in a few seconds, has nearly three-fourths of its outer surface cut away. In other words, when the two cams I1 and 24 are vbrought into a corresponding relationship, these two cams present a cylindrical outer surface; whereas if they are rotated away from this relationship, as will be explained later, they present varying depressed areas at different positions around the axis of the shaft I5.

Supported by the plate I0 and insulated therefrom are the contact arms 28, 29 and 36, constituting the lire-ou. switch 12. The arm 29 has formed on its outer end a shoe 3I which is wide enough to ride on either of the cams I1 and 24 separatelyor on both at the same time depending, of course, upon the relative position. If, for example, the cams I1 and 24 are turned so that the shoe 3| rides upon their depressed areas 32, then the arm 29 contacts with the arm 28, but if the shoe 3| rides upon either or both of the raised areas 33, then the arm 29 contacts with the afm 36. Three identical contacting arms 28R, 29R and 36R are similarly mounted about cams I1 and 24. but the arm 29R rides at a different point on their periphery. These arms constitute refueling switch 13 It is desirable to provide a scale 34 on the front plate I4 on which is indicated the fractions of an hour, indicating the distance in time to the next refueling period. For example, as shown in Fig. 3, the position of the pointer I 6 indicates that the next refueling period will commence one-half hour later.

Rotatablv extending through the plates I6 and I4 is a switch operating drive shaft 35 which has secured thereto a switch operating pin gear 36 which meshes with the gear 23, which it equals in diameter. The gear 36 is driven by the switch operating motor I2 through the reduction gears 21 Loosely mounted on the shaft 35 is a pin gear 31 which meshes with the gear I 8 and equals same in diameter. The pin gears 36 and 31 are socalled because of the fact that the gear 36 has a 75 pin 38 projecting from one side thereof and the gear 31 has a pin 39 projecting into the path of the pin 38.

It will be noted that the paths of travel of the pins 38 and 39 coincide, therefore, if the gear 36 is turned through one revolution, the pin 38 on the gear 36, which is driven by the operating molas shown in Fig. '7, thus holding the switches in their upper or normal positions. The cam I1 is permitted to be advanced in this fashion by the ratchet pawl 26, but as soon as the motion ceases, the pawl 20 reengages the timing motor II which slowly rotates the cam I1 forward from the cam 24 and'moves the driven pin 39 away from the pin 38 which has been driving it.

The front end of the shaft extends through a bushing 46 which is rotatable within the plate I4 for adjustment purposes. On the front end of the shaft 35 is secured a position indicating dial 4I which is provided with a turning knob 42. The dial 4I is frictionally connected to the bushing 40 by means of the spring 43.

Secured to the bushing 40 is a leaf actuating disc 44 which is provided with a notchv 45. Secured to the bushing 48 is an indicator arm 46 whose pointer 41 extends along the outer edge of the dial 4I A fixed indicator 48 is secured to the front plate I4. The dial 4I has marked on the front thereof various positions on the dial which, in conjunction with the indicator 48, will indicate the particular portion of the variable cycle in which the device is operated.

On the rear end of the shaft 35 is secured the position controlling disc 49 from which a segment 50 has been removed. Riding on the face of the disc 49 are four contacting brushes. One of the brushes 5I rides on the disc near its center and makes contact throughout the cycle. The other three brushes are in this case spaced approximately forty-five degrees apart about thel disc near its periphery, and each is insulated from the disc 49 in turn as the open segment 56 passes under it. Of these three brushes the brush 52 will be referred to as the i'lre-ou brush, the brush 53 as the on" brush, and the brush 54 as the refueling brush.

Also secured on the shaft 35 are the stoker motor switch cams 55 and 56. A brush 51 rides upon the cam 55 and a brush 58 rides upon the cam 56. The. brush 58 has a laterally extending arm 59 provided with a contact point 63 which makes contact with a similar point 63 on the brush 51.

For the purpose of illustrating this invention, there is shown a stoker 66, whose motor 6I is placed in the power circuit 62, which is opened or closed by the brushes 51 and 58 through their controlling action upon the contact points 63. There is also indicated a stack 64 in which is placed a thermostat 65 which is arranged to close a circuit through the wires 66 and 61 when the temperature of the stack 64 rises, or open the circuit when the-stack temperature falls. The wire 61 passes through the switch operating motor I 2 through the transformer 68 to the hot side H of the room thermostat 69, whose cold side C is connected to the wire 66. The wire 61 is also connected to the brush 5I. The movable contact M of the thermostat 69 is vjoined by a wire 10 to the on brush 53. The fire-out brush 52 is connected by means of a wire 1I to the contact arm soA 28 of the "fire-out" switch 12, shown in Fig. 5, which as stated is identical with the refueling switch 13.

The contact arm 29 of the nre-out switch 12 is connected to the moving member M of the stack thermostat 65, that is to the wire 61, by means of a wire 14. The contact arm 39 of the fire-out switch 12 is joined by a Wire 15 to the contact arm 29R of the refueling switch 13. The contact arm 28R of the refue1ing"'switch 13 is joined by a wire 16 to the refueling brush 54. The arm 30B. of the refueling switch 13 is joined by a wire 11 to the wire 66.

Between the wire 66 and the wire 18 is connected a wire 18, between the ends of which is placed a leaf switch 19 which is actuated by the leaf actuating disc 44.

On the position indicating dial 4I is indicated the refueling position 88, the on position 8|, and the fire-out position 82. One half of the circumference ofthe dial 4I carries the spaced values 83, 84 and 85. of one-half hour, one hour, and one and one-half hours, ',respectively, these representing the required idle period which must elapse before refueling can occur. That is to say, if it is desired to refuel the fire following every one hour of stoker inoperation, the pointer 41 is set to the character 84 which corresponds with a one hour interval.

The operation of this device centers about the functioning of. two switches. Thev refueling switch 13, operating in conjunction with the stack Ithermostat-65, periodically initiates stoker operation for lire maintenance. "I'he fire-out switch 12in conjunction with the stack thermostat 65 conclusively shuts off the stoker if the fire is out.

The two switches 12 and 13 are time spaced about and actuated by the cams I1' and 24 which revolve about the shaft I5. 'I'he actuated member 3l of each of the switches 12 and 13 bridges across both cams I1 and 24. Consequently, the operation of either of the switches 12 or 13 occurs only when the gaps ln both cams I1 and 24 coincide beneath a switch shoe 3l.

The cam I1 is driven by the timing motor Il at a very slow speed, as stated. This cam is fastened to its shaft I5 to which is also fastened the ratchet pawl arm I9 and the gear I8. Since the pawl arm I9 is driven by the ratchet wheel 26 which is attached to the gear 25 which in turn is driven by the time motor I I, and the gear 25 is free to rotate on the shaft I5, it follows that the timing motor II can drive the shaft l5 at a slow speed in one direction but the shaft I5 can be driven at a higher speed in the same direction by the motor I2 through the action of the gears 36 and 31 and their connecting pins 38 and 39 inasmuch as the gear 31 meshes with the gear I8, which latter gear is secured to the shaft I5.

As stated, the switch operating motor I2 operates at a relatively high speed, namely one` revolution in a few seconds, and this motion is transmitted to the gear 38 and thence to the gear 23 which drives the switching cam 24.

The two cams 55 and 56 and the parts 51 to 59, inclusive, and 63 constitute the stoker motor switch 86while the disc 49 and the parts 5I to 54, inclusive, constitute the position controlling switch 81. The switches 86 and 81 are actuated from the same shaft 35 to which is frictionaily attached the dial pointer 41 and which pointer is fixedly attached to the leaf actuating disc lll which operates the positioning leaf switch \19. The pointer 41 indicates on the scale of the dial 4I the length of time the stoker must remain idle before a refueling operation is initiated.

As stated, the brush 5I rides on the disc 43 near its center and makes contact therewith throughout the cycle, while the brushes 52, 53 and 54 are spaced forty-five degrees apart about the disc near its periphery in the path of the open segment 50. Consequently, the location of the brush which carries the operating motor circuit under any given set of conditions will determine the angular travel of all members attached to the shaft 35. Similarly, the setting of the leaf actuating disc 44 will determine thev angular rotation of the shaft 35 whenever conditions cause the circuit of the operating motor I2 to be completedl through this switch. 'I'he operating motor circuits, referred to, are completed selectively by switches 12 or 13 or thermostats 65 or 69 in response to lapse of time or change of tem-v perature.

There are, therefore, three fixed rest positions of all parts driven directly by the operating motorf I2 as determined by the brushes 52, 53 and 54 on the edge of the disc 49 and a fourth position adjustable by moving the pointer 41 which determines the position lln which contact will be broken by the positioning leaf switch 19. The latter is the position in which the mechanism comes to rest following a normal shut-off of the stoker at the termination of a refueling or thermostat operation (Figure 9).

Next in sequence are the refueling" position, determined by the brush 54, the normal on position, as determined by the brush 53, and the out-fire position, as determined by the brush 52, and so back tothe normal o position, as determined by the leaf switch 13. The Stoker motor switch 86 closes just before the refuel position and opens between the normal on and fire-out positions.

If the resetting ofthe time drivencam I1 has taken place during the normal shutting-oi! of the stoker, then the operating motor I2 is stopped by the opening of the positioning leaf switch 19. The switching cam 24 will stop in position to allow switches 12 and 13 to drop, as shown in Fig. 9. These switches are held urp, however, by the cam I1, which then slowly revolves until the timing motor II has measured off a period of time equivalent to the sett'ing of the pointer 41 on the position indicating dial by which time the stack thermostat 55 would normally be open, i. e., cooling. At the end of this time (as the refuel indicating pointer I6 reaches zero) the switch 13 drops completing the circuit 29R, 28R, 18, 54, 49, 5I, 61,'transformer 63, 51, I2, 61, 14, 29, 30, 15, 29B through the brush 54,

'causing the operating motor I2 to rotate the shaft 35 sufliciently to turn on the Stoker, but not sufficiently to reengage the pins 38 and 39 or to raise the switch arm 29E to a normal position. The operating motor I2 is stopped as soon as the missing segment 58 in the disc 49 comes to the (refue1) positioning brush 54, all parts then being in positions shown in Fig. 6. 1

The timing motor II continues to advance the cam I1 toward the fire-out switch 12, which is positioned angularly from the refueling switch 13 in accordance with the length of time (iire out period) which the stoker may be run before being conclusively shut oiI in the event that there is no fire.

Normally the stack` thermostat 65 will react to the heat generated by theA fire before this period has elapsed, and in closing will form a circuit -through the closed positioning leaf switch 19, 69, 65M61 I2, 51, 68, 61, 5|, 49, 53, 10, 18, i9 until contact between brush 53 and position controlling disk 49 is broken (on position). Since room thermostat contacts H-M parallel 53-49, the motor circuit will be continued which will cause the operating motor I2 to revolve the dial shaft sufciently to turn olf the stoker motor 5I and reset the time-actuated cam I1 and open contacts i0 19 (normal shut-off). Notice, however, that should thermostat contact M now be midway between H and C the stoker will continue to operate, andthe mechanism will, in effect, have responded to a declineof room temperature not l yet of sufilcient magnitude to close M and C.

' The actual position in which the dial BI comes to rest following a normal shut-off is dependent upon the setting of the pointer 41, since the position to which the cam I1 is carried during this Q0 operation will determine the time which must subsequently elapse before this cam can again trip the switch 'I3 and initiate the next refueling period.

In case the fire is out and does notrespond to a *25 refuel operation the stoker will be allowed to run the full re-out period following which the cam I1 will permit the fire-ou switch 'I2 to trip since the cam 24 is not now in position to interfere with this operation. (See Fig. 6.) Y 3|) A circuit is then set up through the dre-out brush 52, 49, 5|, 61, 68, 61, I2, 51,14, 29, 23, 1I, 52, which will cause the operating motor I2 to revolve the dial sulciently to stop the stoker, but not suiliciently to reengage the pins 38 and 39 g5 or to move the fire-out switch 12 back to its normal position. The fact that the switch 13 is reset during this operation is of no consequence, since it is 'not in the circuit. When the dial 4| `comes to rest in the fire-out position, the 40 thermostat 69 cannot again start the 'stoker unless the re is rebuilt or the dial is turned.

manually.

Furthermore, the timing motor being mechanically disconnected from the cam I1 by the roller 22 which releases pawl 20 `from ratchet wheel 26immediately after the switch I2 trips, cannot further advance the cam I1 and in this way reset the fire-ou switch 12.

At any time prior to a refueling operation, cooling of the thermostat 69 until it contacts C will turn on the stoker. This action is brought about by a circuit M, C, 66, 11, 3DR, 29R,"15, 30, 29, 14, 31, I2, 61, 69, 671, 5|, 49, 53, 1|), M, initiated through the thermostat 59 but held through the leaf switch 19 which causes the operating motor |2 to revolve the dial 4l until the missing segment 50 of the disc 49 lies under the second or normal on brush 53 as shown in Fig. 7. Since this brush 53 lies beyond the refueling position, @o the pins 38 and 39 are always engaged before the end of this operation and the cams I1 and 24 are advanced together, thus preventing the refueling switch 13 from tripping. When they come to rest, the cam 24 is in position to hold up the 55 refueling switch 13, but the re-out switch 'I2 is held up only by cam I1 which is in exactly the same position as Yat theV beginning of a refueling period. Therefore, as cam I1 is advanced subsequently by the timing motor II, the time 70 which must elapse before the switch 12 may drop and shutoff the stoker'in case there is no nre, will be exactly the same as when this time is measured from the beginning of a refueling period. m* When the re-outfswitch 12 ydrop it the end of this time, the stoker will be conclusively shut' oif as previously described provided the stack thermostat has not, in the meantime, closed.

In case the lire is burning and the stack thermostat 65 has closed under a rise in temperature, 5 a circuit will be set up for the operating motor I2 when the switch 12 trips that will turn oi the stoker as explained as when the stack thermostat 35 is open after which a new circuit I2, 31, 98, il, 5I, 49, 53, 19, 18, 19, 18, 66, 65M, 61, I2 is set l0 up which continues to energize the motor until thermostat position until the lthermostat 69 is satisfied, whereupon it will be shut off and the cams I1 and 24 reset in the same manner as at 20 the normal close of a refueling period as shown in Fig. 9.

In case thermostat 69 has respondedl to rise in room temperature sumciently so that M is midway between H and C when switch 12 drops 25 and causes a trial cycling, then the dial 4| will come to rest in the normal oil' position and the stoker will remain shut down. 'Thus it will be seen that, in addition toits other improvements, the invention also provides a means of anticipat- 30 ing the action of the room thermostat when the temperature is either rising or falling, a desirable characteristic which makes for more even regl.1\` lation of room temperature.

summarizing, it will be noted that should the 35 thermostat 69 call for heat during a refueling period, it will as soon as the ,stack 94 heats up advance the dial 4| and the position controlling disc 49 to the normal on position without affecting the operation of the stoker. The thermo- 40 stat 39 can turn on the stoker at-any time unless a continuous timed period of Aoperation has failed to raise the temperature of the stack 64 and has caused the mechanism to move to the "fire-out position. The thermostat 99 can turn off the 45 'stoker at any time except during the "refueling period. This operation takes place normally even though the stack 64 may be cold due to the closure of the cams I1 and 24 preventing the fire-out switch 12 from tripping during this 50 operation.

Refueling operation is initiated only after a predetermined period of inoperation asset by the pointer 41 on the position indicating dial 4|. The length of the refueling operation is vari- 55 able, being dependent on the time required'to raise the temperature of the stack 64. The stoker is conclusively shut oi following any continuous predetermined period of Yoperation which does not result in an increase of stack tempera- 00 ture and may be restarted only by rebuilding the re and/or resetting the mechanism.

'I'he stack thermostat, referred to in the above explanation, may be either of the ilxed setting type or of the type which operates on rise 35 and fall of temperature irrespective of value but the latter is preferable. When the latter is used a reasonable lag is provided to insure an effective period of refueling and to prevent the temporary declines in stack temperature which take place 70 during continuous stoker operation due to lhanges in fuel bed or other factors from falsely ringing about a conclusive shut off.

l. in in. automatic stolzer control including stoker actuating means actuated in response to temperature change, combustion change and/or to time, the combination of a means positioned by said actuating means for indicating the operation or inoperation of a'stoker and means automatically positioned for indicating whether inoperation is due tofuliilled requirements of temperature and refueling or to the extinguishment of the fire.

2. The combination with a stoker motor, a motor control circuit including a stack switch, a refueling switch and a re-out switch, of a cam having a portion successively engaging said refueling and fire-out switches, and a second cam angularly ,movable with respect to the first cam and movable to position to render said portion of the first cam operative or inoperative depending upon the position of the second cam, said rst cam moving first to engage the refueling switch and then to engage the fire-out switch,

moving the cams into such angular relationship.l

as not to operate the fire-out switch.v

4. The combination with a stoker motor. a motor control circuit including a stack switch, a refueling switch and a re-out switch, of a slow speed time train and a high speed switching train, including means for causing one member of the high speed train to overhaul one member of the slow speed train and move the members to an initial relationship corresponding with their position at the beginning of a timed period of stoker inoperation, means for'causing the conclusive stopping of both of the trains at the end of a period of timed operation whenever the stack switch has not closed within such period of time.

5. The combination with a stoker motor and its control circuit including a vfire-out switch and a refueling switch, of a. time driven cam having a cut away portion to permit the switches to move to position respectively to cause "the stoker motor to run and to cause the stoker motor to stop, a second cam having a raised portion of such arcuate length as to close the recess in the first cam, andmeans governed by the changes in temperature of the stack for ca g the lowered portions of the cams to coincide to permit the refueling switch to operate and for moving the cams into such relative angular position as4 to prevent the reiuelingV switch from operating.

6. A motor control circuit including a pair of spaced switches, a pair of. cams in position to operate said switches in succession, the first of said cams normally moving at a constant rate so as to operate the first switch, after a chosen its control of an indicator operatively connected to the control mechanism and carrying indicating marks denoting refueling, fire-out, and operation due to a call for. heat, and means including said indicator for changing the operating time of said control mechanism.

8. The combination with a stoker motor and its control of an indicator operatively connected to the control mechanism and carrying marks indicating respectively: the stoker motor is operating in response to time control, the stoker motor is operating in response to thermal control, the stoker motor is not operating because the fire has gone out; and a further indicator for indicating the portion of the chosen time between timed feedngs that remains before the stoker motor will again start to operate in response to time control.

9. The combination with a stoker and its control mechanism offan indicator showing the period between refueling for which the mechanism has been set and a further indicator indicating what portion of such period is still to run, and means including one of said indicators for adjusting the operating time of said control mechanism.

10. An automatic control for a coal stoker comprising a room thermostat having a cold contact and a hot contact and a contact movable between the hot and cold contacts in response to temperature changes, means including circuit connections for causing Ythe stoker to operate when themovable contact engages the cold contact, means including circuit connections for causing the stoker to stop when the movable contact engages the hot contact, timing means for causing the stoker to operate after a definite period of inoperation regardless oi the engagement or disengagement of the hot contact and movable contact, circuit connections prepared by operation of the timing means for stopping said stoker upon a rise of combustion temperature, and circuit means positioned by operation of the timing means for preventing the operation of the last mentioned means when the movable contact is out of engagement with the other contacts whereby should the room temperature be insuiilcient to hold the movable contact of the thermostat against the hot contact during the timecontrolled refueling operation, the stoker motor will not stop upon risc of the stack temperature but will continue to operate as long as the mov-l able contact is floating between the hot and cold contacts, thus anticipating the call for heat which otherwise would be made as soon as the movable contact touched the cold contact.

1l. An automatic control for a coal stoker comprising a room thermostat having a cold contact and a hot contact and a 'contact movable between the hot and cold contacts in response to temperature changes, means including circuit connections for causing the stoker to operate when the movable contact engages Vthe cold contact, means including circuit connections for causing the stoker to stop when the movable contact engages the hot contact, and means positioned in response to engagement oi. the movable contact with the cold contact for stopping the stoker when'the movable contact is subsequently out of engagement with the other contacts whereby if the room temperature has increased sufiiciently to move the movable contact of the thermostat to floating position at the end of said period of thermal controlled fuel feeding, 'the stoker motor -will be shut 0E, thus anticipating the shutting off of the stoker motor by the movable `contact touching the hot contact.

12. -In a switch forl controlling the operation of ya stoker, the combination of a slow speed time train and a high speed switching train including a means vfor causing said high speed train to overhaul and drive said slow train whenthe parts of the two trains reach an initial relationship, means for stopping the high speed train when the parts of the trains in lsaid initial relationship reach a position corresponding with the commencement of, a timed period of stoker inoperation, switch contacts positioned to be closed by said parts when the parts reach a different relationship due to continued movement of the slow speed train from said position, and means for causing conclusive inoperation of both trains at the end of a period of time beginning with the closing of said switch contact.

i 13. The device of claim 12 including means for indicating any portion of the. cycle through which the switch may be passing.

14. In a stoker control system, temperature responsive means for causing the stoker to operate when the temperature reaches a predetermined' value, timingmeans for operating the stoker after a denite period of inoperation due to a lack of temperature change, means actuated by the timing means and the temperature responsive means for indicating the operation or inoperation of the stoker, and means associated with the indicator means for indicating whether operation has been initiated by the time means or the temperature responsive means.

l5. The system of claim 14 in which the indicator means is stopped in one relative position to show that `stoker inoperation is due to the extinguishment of the fire but is stopped in another position to show'that inoperation is due to fullled time or temperature requirements.

16. In a stoker control system including temperature responsive means for operating the stoker according to the heat output required of the stoker, time means for operating the stoker at timed intervals in the absence of any heat requirement, means controlled by said stoker operating means for indicating operation or, inoperation of the stoker and means controlled by the stopping of the stoker for indicating whether the resulting inoperation is due to fullled heat requirements or to the extinguishment`I of the stoker re.

17. In a stoker control system, temperature responsive means for operating a stoker in accordance with the heat required of the stoker, time means for operating the stoker in the absence of temperature change, indicating means controlled by the temperature responsive means and the time means for indicating the operation or inoperation of the stoker, means controlled by the temperature responsive and time means for indicating whether operation has been initiated by temperature requirements or by the time means, further means controlled by the time and temperature responsive means for indicating whether the inoperation of the stoker is due to fulfilled temperature requirements and time operation or to extinguishment of the re.

18. In a stoker control, in combination a thermostat having hot and cold terminals, a pair of relatively movable cams, means constantly driving one of said cams, a multi-position switch placed for actuation by the -combined action of said cams, said action being dependent upon a predetermined co-relationship of said cams and upon a predetermined angular position of each of them, circuit connections between the thermostat and switch and including electromotive means for moving the other cam to change said co-relationship, said electromotive means being energized in response to certain positions of said switch and in combination with certain positions of the thermostat.

19. 'I'he combination with a stoker motor and its control circuit including a room thermostat having a leaf movable between hot and cold terminals, and means for. keeping the re alive by causing periodic feeding of fuel and air in absence of calls for heat, of a second control circuit including normally open contacts adapted to be closed by an increase in stack temperature and also including the leaf and hot terminal of said room thermostat whereby said second control circuit is adapted to be closed by an increase in stack temperature when acconipanied by an increase in room temperature and in closing to cause the rst circuit to stop the stoker motor and terminate a refueling operation, so that should the leaf be floating between the terminals upon increase of stack temperature at' the end of a normal refueling period the motor will not stop but will continue to operate the stoker until the leaf engages said hot terminal, thus anticipating a call for heat by the room thermostat.

LAWRENCE R. TEEPLE. 

